Urban River Design: A River Restoration Case Study

Abstract

Human excessive requirements on functions of aquatic ecosystems cause that surface waters often suffer from significant morphological and hydrological alterations. Human induced hydromorphological changes of rivers belong among the most common ecological problems of the water bodies and they appear in all scales of river habitat. These changes have an impact in their ecological status and need to be solved in the near future. Successful sustainable river rehabilitation depends on the identification and understanding of key processes and anthropogenic stressors. These factors enable to estimate a proper longitudinal and lateral riverine system structure including stream habitat improvements at different scales. The article summarizes the basic principles of urban river restoration, that enables to approach to the state of dynamic stability and to increase the "absorbing capacity" of freshwater ecosystem. The authors also provide the background facts and principles of the restoration design of canalized reach of the River Trnavka, which flows through an urbanised part of the city Trnava. The Trnavka River has regulated flow regime affected by operation of Boleraz reservoir located 14 km in upstream direction. The river channel capacity equals to 50 m3.s-1 with return period 100 years and ecological flow is Q=0,150 l.s-1. The heavily modified nonprismatic channel has stone and concrete stream banks. The authors have proposed increasing sinuosity of low flow channel and decreasing capacity of the oversized channel by using gravel matraces with planting different types of macrophytes. The main goal of the proposed river restoration measures was to increase aesthetic value of complex restoration design of close public space (the Rose Park) and to implement technical and biotechnical measures that may improve ecological conditions and management operation of the Trnavka River.